Commitments and Contingencies - Future Minimum Lease Payments (Detail) $ in Thousands	Dec. 31, 2017 USD ($)
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2018	$ 16,389
2019	16,626
2020	17,557
2021	17,844
2022	13,519
Thereafter	32,645
Total	114,580
Subleases
2018	310
2019	39
2020	0
2021	0
2022	0
Thereafter	0
Total	349
Net
2018	16,079
2019	16,587
2020	17,557
2021	17,844
2022	13,519
Thereafter	32,645
Total	$ 114,231